Process of eliminating color from caustic alkali



I New York city, New

- v No Drawing.

TENT Fi 'lC.

THOMAS C. MEADOWS AND HERMAN D. RUHM, OF NEW YORK, N. Y., ASSIGNORS T0 EASTERN PDQ-ASH CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW PROCESS OF ELIMDYATING COLOR FROM OA'USTIO AALI.

'- To all whom it may concern .7

Be it known that we, THOMAS C. MEADOWS, a citizen of the United States, residing in York, and HERMAN D. RUHM, a citizen of the United States, residing in New York city, New York, have invented certain Improvements in Processes of Eliminating Color from Caustic Alkali, of which the following is a specification.

The object of our invention is to remove discolorations from fluid bodies of concentrated caustic alkali, an object which we attain by subjecting such bodies to the bleaching action of an electric current passed through the same.

In the production of strong concentrated solutions or molten bodies of caustic potash or other caustic alkali great difliculty has been experienced in obtaining a colorless product because of the avidity with which such concentrated fluid body of caustic potash attacks organic matter or mineral compounds of different kinds with which it is brought into contact and which have a stainmg or discoloring effect upon it, and the same true of other caustic alkali.

We have discovered that by passing a current of electricity through such concentrated solution of caustic alkali, or through the caustic alkali while. it is in a state of fusion or otherwise fluid, all discolorations will be removed and a bleached or colorless product will result. i

In view of the limited knowledge existing as to exactly what electricity really is, it is impossible to give a positive explanation of the nature of the action of the electric current when so employed. It is possible that the small amount of chlorides almost always present in caustic potash are electrolyzed and hypochlorites formed, or chlorine liberated, acting on the coloring matter in the ordinary manner of hypochlorites, or chlorine, when used as a bleaching agent. Again it may be Specification of Letters Patent. v

Patented May 9, 1922.

Application filed January 25, 1919. Serial No. 273,129.

mg agent, or it may be that the coloring matter itself is an iron or other compound which iselectrically disassociated by the electric current so that the objectionable color disappears. On the other hand, it is possible that the true explanation may be even different. We only know, positively, that which takes place but not the reason therefor.

- A preferable method of applying the current is to connect to one pole of an electric generator the vessel in which the solution is contained or in which the alkali is fused, so that said vessel acts as a cathode, and to in-' sert into the fluid contained in said vessel an anode of platinum, carbon, graphite, iron oxide or other available anode material, or even the bare copper wire or other conductor connected to the other pole of said generator, the strength of the current being regulated as desired and the treatment being continued until the desired bleaching effect has been produced.

e are aware that it is a common practice to pass an electric current through a saline solution in order to effect the decomposition of the latter and the freeing of chlorin gas therefrom, or for the purpose of causticizing such saline solution, but our invention is. as will be apparent, essentially different from this, in that it is for the correction of a defect arising from the concentrated form of an alkaline fluid previously rendered caustic.

We therefore claim- The mode herein described of eliminating color from fluid bodies of concentrated caustic alkali, said mode consisting in subjecting such bodies to the bleaching action of a current of electricity passed through the same.

In testimony whereof, we have signed our names to this specification.

THOMAS C. MEADOWS.

HERMAN D. RUHM. 

